F22a head on f23 block machine work question

[Timoteo]

Hey so i was wondering the f22a head is made for an 85mm bore and the f23 block has a 86mm bore. Has anybody done the frankenstein build and had the combustion chamber machined .5mm bigger all around to match the 86mm bore? Does anybody know what the name of this process is called?

[deevergote]

The bore mismatch shouldn't be all that big a deal. A number of factory head/block combinations aren't perfectly matched.

If you want to have it done, call a machine shop and ask them. They'll not only tell you the name of the process, but they'll also be able to tell you how much it will cost, and whether or not it's a good idea. One thing you definitely don't want to do is compromise the head gasket seating area.

[CornDog]

You can try chamfering it. .5 mm isn't much but maybe a Dremel and a fine drum sanding bit might do the trick. As far as machining goes, I have no idea.

[CB7Denmark]

The #1 King of N/A has that exact build and is pulling unbelievable numbers, as far as I know, he does not have or had any issues related to the difference in the bore (neither with the HG), and I feel like the person in question would have shared his problems as he seems to do with everything else.

[deevergote]

I think I may have been largely responsible for the panic regarding combustion chamber / cylinder bore mismatch in this community. I foresaw a problem regarding pre-ignition that could've come from the sharp combustion chamber edges as they protruded beyond the edge of the cylinder wall, but it seems there really is little need for concern.

[Timoteo]

I think I may have been largely responsible for the panic regarding combustion chamber / cylinder bore mismatch in this community. I foresaw a problem regarding pre-ignition that could've come from the sharp combustion chamber edges as they protruded beyond the edge of the cylinder wall, but it seems there really is little need for concern.

Yup you were lol. I stopped messing with cars for a while because they are expensive but recently ive been wanting to pick up a cb7 for some better gas mileage and because i really want to build something bad. I know i could pick up one of those blocks cheap and easy and it looks like it jump the c/r from 8.8:1 to 9.3:1. How do you think this setup would run without a tune? I figured id have tune it right away but you guys may have some better insight

[Jarrett]

How do you think this setup would run without a tune? I figured id have tune it right away but you guys may have some better insight

It will probably feel like a marginal gain over a standard F22A. As long as you use an OEM camshaft, I wouldn't bother with tuning. The additional volume of air is well within the factory ECU's ability to compensate for, but a wideband O2 wouldn't hurt. Something like an AEM UEGO would be nice insurance.

[Timoteo]

It will probably feel like a marginal gain over a standard F22A. As long as you use an OEM camshaft, I wouldn't bother with tuning. The additional volume of air is well within the factory ECU's ability to compensate for, but a wideband O2 wouldn't hurt. Something like an AEM UEGO would be nice insurance.

Whats an AEM UEGO?

[deevergote]

http://www.aemelectronics.com/produc...uego-afr-gauge

[CB7Denmark]

I think I may have been largely responsible for the panic regarding combustion chamber / cylinder bore mismatch in this community. I foresaw a problem regarding pre-ignition that could've come from the sharp combustion chamber edges as they protruded beyond the edge of the cylinder wall, but it seems there really is little need for concern.

But you're absolutely right that sharp edges promotes detonation, the edges can be slightly sanded so they are smooth to the touch, thus eliminating detonation.


Funny thing, the Mahle Goldseries has a, and I'm not kidding, KNIFE sharp edge around the 10cc dome, which I will be treating as well.